JavaScript

• JavaScript is not technically considered a programming language. Rather, JavaScript is purely a scripting language that allows an HTML developer to add processing functionality to a Web page. JavaScript can react to input and display output on a Web page. A script is written directly into the HTML and is interpreted by the user's Web browser at the same time as the HTML. Despite the name, JavaScript is not related in any way to Java, the programming language, and was only so named for marketing reasons.
  
  

Java Applets

• Java is a programming language developed to run in a virtual machine. This allows Java applets, small independent programs designed for a single task, to be run on almost any platform that has a Java virtual machine installed. This creates a liaison between the program and the environment. A programmer would only have to develop one version of the program and any platform with a virtual machine would be able to run that program. Java must be compiled into machine language before it can be used. When used in conjunction with HTML, the HTML does nothing more than call the applet, sending it to the client computer. The client computer loads the applet into the virtual machine in order for it to be run.
  
  

Usage

• JavaScript is often scattered throughout an HTML page. The script can be stepped in and out of as needed. JavaScript is also aware of the Web page it exists in and can be used to monitor and make changes based on page activity. For instance, a script can watch for the user to press a button. The script is aware of the button press and can act on it, sending an email or changing the background color. Java Applets have no interaction with the browser or the HTML. The HTML simply calls the applet and steps back. Java Applets can also be run independently from a browser, while JavaScript cannot. Since Java is a fully functional programming language, it can also be used to create graphics and special effects. It is most often used in the creation of online browser games.
  
  

Requirements

• Java applets require the Java virtual machine to be installed on the client computer. The virtual machine can also be integrated into most modern browsers, giving them the ability to download and run applets right in the browser. JavaScript only needs a browser with a JavaScript interpreter, which most have out of the box.